The present invention relates to a fuel injection pump for internal combustion engines.
More particularly, it relates to a fuel injection pump which has a drive shaft extending into an inner chamber and connected by a front face coupling with a front cam plate which sets a pump plunger into a reciprocating and rotating movement with the cam plate running on rollers of a roller ring, and a rotational angle sensor is provided in the pump. Such a fuel injection pump is known from the DE-OS 33 36 871, in which the fixed sensor part is directly and firmly fixed to the roller ring and lies radially opposite the sensor wheel on the drive shaft. For purposes of centering, the fixed sensor part can be displaced and re-fixed in the circumferential direction on the roller ring. This solution has the disadvantage that there is play between the roller ring bearing and the fuel injection pump housing, allowing movement of the roller ring in its radial plain, when forces act upon it when cams of the cam plate ride up on the rollers. Due to the fact that the roller ring is adjustable via the injection timing bolt, the bolt represents a one-sided bearing point for the roller ring, so that when it is loaded by forces in its circumferential direction, the roller ring carries out tipping movements around the bolt fulcrum. Moreover, the bolt fulcrum itself also has play, and the bolt itself can give to a certain extent, via the injection timing gear, when loaded by forces at right angles to the length of the bolt. On loading of the roller ring, its fulcrum additionally performs a movement in the circumferential direction. Where the stationary sensor part is fixed on the roller ring, it performs this movement in unison with the roller ring. For reasons of space and accommodation, the stationary sensor is usually arranged diametrically opposite the fulcrum point of the bolt. In this region, the movement components of the roller ring are greatest during its movement around the bolt. This then results in unintentional or erroneous measurements due to the fact that the stationary sensor part actually moves in a circumferential direction around the sensor wheel, and this causes incorrect timing of the fuel injection commencement. Depending on operating conditions, this error accumulates, either positively or negatively, causing the measuring result and the resultant injection commencement timing to be affected with an uncontrolled error. If the logging of the revolutionary speed, which is required for the volume calculation, lies within the relevant range, then this angle error has the effect of an error in the revolutionary speed, in turn making the volume calculation wrong.